Prune repository for Haskell only

[LKedward]

• Update README with archive notice and Haskell instructions
• Remove Fortran fpm sources
• Move Haskell sources back to directory root
• Transfer Haskell-fpm issues and mark wontfix
• Prune CI workflow for Haskell fpm only
• Update manifest reference to only describe Haskell fpm

[certik]

I haven't checked every change very closely, but I agree with the goal and direction. Fine to merge as far as I am concerned.

[awvwgk]

What about the manifest reference, this document should be maintained exclusively in the main fpm repository to avoid confusion.

[LKedward]

What about the manifest reference, this document should be maintained exclusively in the main fpm repository to avoid confusion.

Good point; I think we should edit the manifest reference in this repository to only describe Haskell fpm, and then remove references to Haskell fpm in the main repository manifest reference.